As explained in a brochure entitled "Environmental Systems" available from Tensar Environmental Systems, Inc., a subsidiary of The Tensar Corporation ("Tensar") of Atlanta, Ga., the disclosure of which is incorporated herein in its entirety by reference, there are products presently available on the market that enable a fast and economical construction of a waste containment facility which provide maximum capacity for storage of waste materials. Typically, these waste containment facilities, or landfills as they are more commonly referred to, are formed by excavating a pit to a predetermined depth with inclined sidewalls tapering downwardly towards a flat or inclined base.
In many situations, the slope of the sidewalls of such a facility is initially limited by the strength of the earth or soil forming the landfill. The more gradual the slope of the sidewalls, the less landfill space available for a given footprint. Since the availability of landfill space is decreasing, the capacity of each landfill must be maximized. Uniaxial and biaxial geogrids manufactured by The Tensar Corporation can be used to build stable reinforced soil slopes at steeper slope angles, thereby improving site utilization and landfill capacity. For example, a conventional unreinforced soil slope having a ratio of 2.5:1 may be increased to a 1:1 ratio by providing such reinforcing materials in the landfill sidewalls.
Obviously, the most efficient use of a landfill site would be one with vertical sidewalls. However, a further limiting factor on the slope of landfill sidewalls heretofore has been the need to secure liner materials, which are necessary to prevent escape of leachate from the waste material, against slippage. Sidewalls of a landfill are lined with sheets of polymeric material or other impermeable material to form a barrier against such contamination. Layers of geogrid and geofabric material are commonly placed interiorly of the liner to aid in conveying leachate to the bottom of the landfill for transfer to a collection system.
The angle of the sidewalls of a waste containment facility are, therefore, limited to a slope beyond which the various layers of the liner system would tend to slip, thereby allowing leachate to escape and possibly contaminate the ground water. For this reason, even when a waste containment site with stable vertical or near vertical sidewalls is available, such as in a rock quarry or the like, sloped sidewalls must be provided by further excavation or adding fill to protect against slippage of the liner materials. Alternatively, the liner materials must be secured to the vertical or steeply sloped sidewalls by rock bolts or the like, a costly procedure which introduces additional problems by necessarily piercing the liner material thereby destroying its integrity.